1. Field of the Invention
The present invention relates to a positive resist composition and a resist pattern formation method using the same.
Priority is claimed on Japanese Patent Application No. 2004-142581, filed May 12, 2004, the content of which is incorporated herein by reference.
2. Description of Related Art
In recent production for semiconductor elements or liquid crystal elements, miniaturization has been rapidly advanced by progress of lithography techniques. For this miniaturization, the wavelength of the light source for the exposure has been shortened generally. Specifically, KrF excimer lasers (248 nm) are now used; furthermore, ArF excimer lasers (193 nm) are about to be introduced, while ultraviolet light as represented by g-line and i-line has been used in the past.
A chemically amplified resist composition is known as one of the resist materials which satisfy the conditions for the resolution being high enough to reproduce the miniaturized pattern. The chemically amplified resist composition is composed of a base resin whose alkaline solubility changes by an action of an acid, and an acid generator which generates an acid by the exposure, and both are dissolved in organic solvent.
Generally, a polyhydroxystyrene type resin, some of whose hydroxyl groups are protected by acid dissociable dissolution inhibiting groups, is used as a base resin in the chemically amplified positive resist composition which is proposed as the preferable resist material for the exposure method using KrF excimer lasers (for example, see patent document 1).
As the acid dissociable dissolution inhibiting group, a so-called acetal group including a linear ether group as represented by a 1-ethoxyethyl group and a cyclic ether group as represented by a tetrahydropyranyl group, a tertiary alkyl group as represented by a tertiary butyl group, or a tertiary alcoxycarbonyl group as represented by a tertiary butoxycarbonyl group is mainly used.
In recent years, the improvement of the resolution of the resist material has been keenly sought, as the speed of the miniaturization is being accelerated. In addition, the resist pattern with high cross sectional rectangular formability and favorable shape has also been keenly sought.
However, as the needs of the resolution and favorable shape of the resist pattern become severe, the problems occur in that the conventional chemically amplified positive resist composition cannot be sufficiently compatible with these needs. Specifically, it is difficult to simultaneously achieve the high resolution, favorable shape, and the wide depth of focus of the resist pattern.
[Patent document 1] Japanese Unexamined Patent Application, First Publication No. Hei 4-211258